Liquid-cooled electric apparatus



Sept. 17, 1940. M Q, TRQY 2,214,865

LIQUID-COOLED ELECTRIC APPARATUS Filed Feb. 25, 1939 Inventor: Matthew 0. Troy,

is Att, orn ey.

Patent ed Sept 17, 1940' LIQUID-COOLED ELECTRIC APPARATUS Matthew 0. Troy, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application February 25, 1939, Serial No. 258,478

2 Ohlms.

The present invention relates to electric devices such, for example, as transformers which are provided with a body of liquid insulating and cooling material. It is the object of my invention to im- 5 prove the eificiency and decrease the cost of such devices.

It is highly desirable that liquid insulating and "cooling materials in electric devices should be non-inflammable and should be substantially incapable of yielding by decomposition inflammable or" explosive gases. These properties, combined with other desirable properties, are found in liquid halogenated compounds such, for example, as chlorinated diphenyl, chlorinated benzene. chlorinated naphthalene, chlorinated phenyl benzoate, chlorinated benzotrifluoride, and various mixtures of such compounds. Examples of such compositions are described in U. S. Patents 1,931,455 of October 17, 1933, 1,999,004 of April 23,

1935, and compositions of this type not only are relatively expensive, but also are somewhat volatile when heated. It is desirable to use such compounds in as small amount as is consistent with efficient service to provide efiicient cooling means therefor and to prevent evaporation losses.

In accordance with my invention these conditions are fulfilled by providing one or more suitable auxiliary superimposed sealing liquids having lower specific gravity. The lowermost layer of cooling agent in a transformer, or other electrical device, in which the electrical parts are immersed, preferably consists of abody of halogenated, non-inflammable insulating composition. The electrical parts, such as transformer coils,

may be covered with cotton or paper which is permeated by the halogenated material. Chlorinated compounds of aromatic hydrocarbons are suitable for use as cooling agents. Such compounds in general have a high specific gravity.

4O Superimposed thereon are one or more layers of lighter liquids which are insoluble in the insulating composition and function to both seal and cool the latter. The superimposed sealing layer need not be electrically insulating.

The accompanying drawing is a vertical section of 'a transformer illustrative of my invention.

The sealing and cooling material advantageously, but not necessarily, may be vaporizable at the normal working temperature of the electric de vice, or at least at a more elevated temperature which is not deleterious to such device. Water is an example of such a sealing material. Its boiling temperature of 100 C. becomes the limiting temperature of the lower insulating liquid. The

insulating liquid hence does not become heated above the permissible temperature to which organic insulation immersed therein may be exposed. Water is substantially insoluble in chlorinated hydrocarbons and, of course, does not add to the cost of an electrical installation. 5

Monohydric alcohols, such as methyl alcohol boiling at 66 C., ethyl alcohol boiling at 78 C., also may be used as sealing materials. Polyhydric alcohols, such as ethylene glycol boiling at 197 C., and glycerine boiling at 290 C., also are 10 usable as sealing agents in accordance with my invention. Paraflin wax, cellulose acetate and ethyl cellulose are examples of less volatile materials which are capable of use as sealing agents.

As shown in the drawing, the apparatus in- 15 cludes a tank I containing a magnetic core 2 and inductive windings 3, the terminal conductors for which, as indicated at 4, enter the tank below the upper level of the relatively dense, non-inflammable liquid insulating material 5 of the type 20 above described. The insulating liquid may consist, for example, of a suitable mixture of hexachlor diphenyl and trichlorbenzene. Above the insulating liquid 5 is a body 6 of suitable heatabsorbing and sealing material. Above the seal- 25 ing body 6 there may be provided, if desired, a thin layer 1 of still lighter relatively non-volatile material, such as ordinary mineral oil. A vent 9 is provided for the escape of vapor.

As shown in the drawing, automatic means may 30 be provided, if desired, for replenishing the material G, assuming a liquid to be used. The particular apparatus illustrated, which, of course, may assume a variety of forms, consists of an auxiliary tank It) which communicates with the main 35 tank by a conduit H having an inlet l2. Hence, the level of the liquid [3 in the tank I0 is the same as the level of the liquid 6 in the main tank I. Should the level of the liquid l3 fall materially, then the float valve It opens and permits liq- 40 uid from the reservoir Hi to flow by gravity through the conduit l6 into the auxiliary reservoir l0, and from thence replenishes the liquid body 6 through the conduit H. A sight glass I! may be provided to give visual indication of the 5 liquid level. A conduit 18 may be provided which communicates both with the main and auxiliary tanks to permit of equalization of gaseous pressure in the spaces above the liquid contents. This .conduit may be provided with a vent valve I9 50 When water, monohydric alcohol, or other volatile sealing liquid, is used to cover the insulating liquid 6, then one of the important functions of such sealing liquid is its capacity of absorbing excess heat during temporary overloads of termed that of a heat brake. This function is facilitated both by the relatively large bulk of the sealing liquid, and by theboiling of this liquid should the temperature rise as. high as its boiling point. When a high boiling liquid, such as a polyhydric alcohol, is used, the capacity of the heat brake, of course, is limited by the heat capacity of such liquid as the temperature ordinarily would not be permitted to rise to its boiling point. In either case, however, the superthe electrical device, a function which may be in the described apparatus without departing from my invention. For example, not only may the automatic replenishing device be omitted, but also the cover 20 for the tank I may be omitted.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The combination of an electric transformer,

a container therefor, a liquid chlorinated organic compound surrounding and insulating said device and a heat brake comprising a relatively large body of immiscible lighter liquid having a higher specific heat superimposed on said chlorinated compound, said material being volatilizeble at temperatures too low to injure said device.

2. An electric transformer comprising a tank, inductive elements therein, a body or liquid helogenated hydrocarbon surrounding said elements,

and a heat brake comprising a relatively large body or Water superimposed on said hydrocarbon.

MATTHEW O. TROY. 

